The present invention relates broadly to two or more layer tubular polymeric laminates or composites and to articles such as tubing and hoses constructed thereof, and more particularly to tubular polymeric laminates or composites formed of a layer of a thermoplastic fluoropolymer material bonded directly to a layer of a more general purpose thermoplastic resin material which may be a nylon or other polyamide.
Fluoropolymers are known to exhibit exceptional resistance to chemical degradation and vapor permeation. Accordingly, these materials are desirable for use as liners in tubing, hoses, and other conduits such as for conveying fuel or fuel vapor in automotive, aerospace, or marine applications, or for conveying petroleum and other hydrocarbons and organic or inorganic solvents in a variety of transport, motion control, natural resource recovery, and chemical process applications. However, fluoropolymers also known to have low surface energies and high electronegativites which, although contributing to the lubricity and xe2x80x9cnon-stickxe2x80x9d properties of such materials, often makes the bonding of other materials thereto difficult.
Heretofore, conventional techniques for laminating polyamides, polyurethanes, and other common polymeric materials to fluoropolymers has been to etch the surface of the fluoropolymer by treatment with a chemical, such as a solution of sodium or other alkali metal in anunonium, an amine, or other solvent, or with a plasma. In general, such treatments, which are further described in U.S. Pat. Nos. 2,789,063; 5,062,456; and 5,653,266, and in Benderly, A. A., J. Appl. Polym. Sci., 6(20), 221-225 (1962), and Schonhorn, H., Hansen, R. H., J. Appl. Polym. Sci., 11, 1461-1474 (1967), are known to be more effective when the fluoropolymer contains reactive chemical groups. Other methods of bonding PTFE and other fluoropolymers, and the use of such methods in the manufacture of articles such as tubing and ion exchange members, are described in U.S. Pat. Nos. 6,016,848; 5,653,266; 5,599,614; 5,141,800; and 4,954,388, and in International. (PCT) Publ. No. WO 95/16730.
Another technique, often used in the construction of multi-layer tubing for fuel line applications, involves the provision of a bonding or tie layer between an inner fluoropolymer layer or liner and a second layer of a stronger, tougher, and, typically, less-expensive material, such as a nylon, polyamide, or polyurethane, which is used as a reinforcement or cover for the liner. The tie layer, which may be formed as a co- or tri-extrusion with the liner and second layers, is formulated to be compatible chemically with both the fluoropolymer material of the liner and the material of the second layer such that a thermal fusion bond may be achieved between the liner and tie layer and the tie layer and second layer to thereby consolidate the tubing into an integral structure. The use of such tie layers dictates the selection of specific materials for the liner and second layer so as to be compatible with the material of the tie layer, or vice versa, and is believed limited to the use of melt processible fluoropolymers such as polyvinylidene fluoride (PVDF) or ethylene tetraflurorethylene (ETFE). The use of tie layers in the bonding of multi-layer tubing constructions is described further in U.S. Pat. Nos. 6,066,377; 6,041,826; 6,039,085; 6,012,496; 5,996,642; 5,937,911; 5,891,373; 5,884,672; 5,884,671; 5,865,218; 5,743,304; 5,716,684; 5,678,611; 5,570,711; 5,566,720; 5,524,673; 5,507,320; 5,500,263; 5,480,271; 5,469,892; 5,460,771; 5,419,374, 5,383,087; 5,284,184; 5,219,003; 5,167,259; 5,167,259; 5,112,692; 5,112,692; 5,093,166; 5,076,329; 5,076,329; 5,038,833; 5,038,833; 4,706,713; 4,627,844; and 3,561,493, in German Patent Publ. Nos. DE 4001126; 3942354; and 3921723; and 3821723, in Japanese Patent Publ. Nos. JP 61171982; 4224939; and 140585, in Europe Patent Publ. Nos. EP 1002980 and 551094, in International (PCT) Publ. Nos. WO 99/41538; 99/41073; 97/44186; and 93/21466, and in U.K. Patent Publ. No. GB 2204376.
More recently, and as is described further in European Patent Publ. No. EP 992,518, modified fluoropolymer materials have been developed which may be fusion bonded, such as by co-extrusion or molding, to polyamides and epoxies. Such materials are formulated as a fluororesin copolymer having terminal carbonate end groups.
The fluororesin copolymer may comprise, based on the copolymer, between about 30-81 mole % of a tetrafluoroethylene (TFE) monomer, and about 19-70 mole % of at least one other monomer. A preferred composition is a terpolymer of about 40-81 mole % TFE, 6-43 mole % ethylene, and 10-30 mole % of hexafluoropropylene (HFP), and in that regard may be characterized as a modified ethylene tetraflurorethylene (ETFE) copolymer or as an xe2x80x9cEFEPxe2x80x9d (ethylene-perfluoroethylene) copolymer. The composition also may contain 0-10 mole % of a fluorovinyl compound. The carbonate end groups, which may be incorporated into the copolymer chains by the use of a peroxycarbonate polymerization initiator, may be considered an activator in having a high reactivity with the polyamides bonds and/or terminal amino or carboxyl groups of materials such as polyamides.
Advantageously, these modified fluoropolymer materials are able to be fusion bonded, such as by co-extrusion or molding, to a general purpose resin such as a polyamide or epoxy at a temperature below the thermal decomposition temperature of the resin, and preferably at a temperature within the range of between about 150-260xc2x0 C. other otherwise within the range of the preferred fusion bonding temperature of the resin. In this regard, the fluororesin copolymer may be formulated to have a melt viscosity which allows flow of the copolymer within such temperature range. Modified fluoropolymer materials of the above-described type are sold commercially by Daikin America, Inc. (Orangeburg, N.Y.) under the designations Neoflon(trademark) RP-5000 and RP-5000AS Series.
It is believed that tubular polymeric composites of two or more layers including a fluororesin layer fusion bonded directly to a nylon or other amide or general purpose resin layer would be useful as elements in a variety of hose and tubing constructions. In this regard, in severe or even normal service environments, such as in mobile or industrial hydraulic and pneumatic applications, or in crude oil and other energy recovery applications, hoses and tubing of the type herein involved may be exposed to a variety of environmental factors and mechanical stresses that cannot always be predicted. It is anticipated, therefore, that tubing and hose constructions which offer chemical and/or moisture resistance, but which are still economical would be well-received by numerous industries for use in high pressure and other fluid transfer and motion control applications.
The present invention is directed to polymeric composites and articles such as tubing and hoses constructed thereof. More particularly, the invention is directed to a two or more layer tubular composite which may be formed by fusion bonding, such as by extrusion, co-extrusion, or molding. In being formed of a layer of a thermoplastic fluoropolymer material which may be bonded directly, i.e., without the use of an adhesive or tie layer, to a layer of a more general purpose thermoplastic resin material which may be a nylon or other polyamide, the composite of the invention is particularly adapted for use as a core tube in a reinforced hose construction, and as tubing for vehicular airbrake systems and other applications requiring chemical and/or environmental resistance. Typically, the fluoropolymer material layer, which may be both chemically and environmentally-resistant, is provided as an innermost or outermost layer of the composite structure or member and of the article constructed thereof.
In a representative hose embodiment, the composite structure of the invention may be formed as having an inner fluoropolymer layer, and an outer nylon or other resin layer bonded directly to the fluoropolymer layer. The structure so formed may be used as a core tube over which one or more layers of a fibrous reinforcement layer are braided or wound to provide resistance to internal pressure, such as in the case of a medium or high pressure, i.e., 150-60,000 psi (1-413 MPa), hose construction, or to external pressure such as in the case of a collapse-resistant hose for oil recovery, vacuum, or other applications. Advantageously, the inner fluoropolymer layer of the composite structure may form the innermost layer of the hose and thereby provide internal chemical resistance. Also, the composite structure of the invention, as formed as having an inner and/or outer fluoropolymer layer, alternatively or in addition to the core tube may be provided between a cover, which itself may be the nylon or other resin layer of the composite or a polyurethane or other layer surrounding the composite, and the reinforcement layers of the hose so as to provide resistance to the penetration of external moisture or chemicals.
In a representative tubing embodiment, the composite structure of the invention may be formed as having an inner nylon or other resin layer, which may be reinforced or unreinforced, and an outer fluoropolymer layer bonded directly to the resin layer. The structure so formed may be used, either as coiled or uncoiled, as tubing such as for tractor/trailer airbrake systems. Advantageously, the outer fluoropolymer layer of the composite structure may form the outermost layer of the tubing and thereby provide external chemical resistance such as against methanol and other solvents and corrodants which may be used in the cleaning of the vehicle.
The present invention, accordingly, comprises the structures and article constructed thereof possessing the combination of elements which are exemplified in the detailed disclosure to follow. Advantages of the present invention include a tubular composite structure which may be used alone as tubing or as core tube in combination with other materials in a multitude of hose arrangements to provide resistance to internal and/or external chemicals and moisture. These and other advantages will be readily apparent to those skilled in the art based upon the disclosure contained herein.